The study of foraging behaviour of 20 forest bird species was conducted during two different phenophases of a vegetation period in the West Carpathians oak-dominated natural forests. Using a standard and a modified a priori approaches, seven foraging guilds were distinguished, whereas only five significantly different guilds were clustered by a a posteriori approach. Four common guilds for all three approaches were quantitatively compared. The methods differed especially in the classification of foraging generalists. Differences in guild densities between a priori and a posteriori approaches emerged in both, the pre-foliage and the foliage periods, chiefly in the guilds of insectivores on ground surface (47.3–89.6%) and insectivores on buds/leaves and twigs (15.0–45.9%). The modified a priori method provided moderate densities of separate guilds. The modified a priori method with more detailed density calculation is recommended for the quantitative guild structure comparisons of different bird assemblages. The method takes into consideration proportional use of foraging substrates in combination with food type.
Black-backed jackals (Canis mesomelas, Schreber, 1775) survive in a wide range of environments. Their foraging strategies are highly variable in different habitats. Adaptations in foraging behaviour in relation to abundance and quality of food sources are expected to be highly pronounced in an extreme habitat like a desert. This study investigated the diet composition in black-backed jackals in the Namib Desert by analysing faecal samples collected between February 2004 and August 2005. Frequency of occurrence, relative dry mass and proportion of biomass consumed were calculated for different prey items. Insect parts, mainly of two species – the giant longhorn beetle (Acanthophorus capensis) and a locust (Anacridium moestum) – were found in 72.2% of the samples and were estimated to have contributed 22% to the biomass consumed. Mammals, predominantly rodents and ungulates, represented the highest proportion of biomass consumed (42%), although their remains were found in only one third of the samples. Based on biomass, mammals are assumed to be the jackal’s preferred prey, but, probably due to lower abundance, more diffi cult to obtain than insects. More than 50% of the samples contained plant material, mainly seeds of !NARA plants (Acanthosycios horridus) and false ebony (Euclea pseudebenus), especially during their fruiting seasons. Although the abundance of A. capensis and of A. moestum varied annually, their remains were found in scats throughout the year, indicating a certain degree of specialization on these prey species.
Many insect species attracted to fermenting sap often fight for access to this resource, which results in the establishment of interspecific dominance hierarchies. In one such system, the hornet Vespa mandarinia (Hymenoptera: Vespidae) behaviourally dominates during the daytime and several subordinate species avoid aggressive interactions in various ways. In order to elucidate the interspecific variation in competitor-avoidance behaviour and its subsequent effect on foraging success, the behaviour of species of hornets, beetles and butterflies at patches (exudation spots) in Japan was recorded. The percentage of individuals that succeeded in visiting a patch following departure from one, or an attempted visit, or after waiting near a patch for >= 10 s, did not differ greatly among species, despite the distinctive differences in dominance between V. mandarinia and the other species. These results suggest that subordinate species may be equally effective at foraging for sap as the dominant species. The competitor-avoidance behaviour differed among the species. Vespa crabro and satyrine butterflies mainly avoided competition by actively moving away from competitors. The beetle Rhomborrhina japonica (Coleoptera: Scarabaeidae) often remained close to an occupied patch and waited for the occupant to leave, whereas V. ducalis and nymphaline butterflies used both tactics. The different costs associated with fighting or flight may have determined the differences in the foraging tactics of the species studied and behavioural switching in those species utilising both tactics.